Remote controlled model cars and other model vehicles have been a realty for some time. Racing hobby grade or upscale model vehicles has become a nationwide pass-time resulting in constant efforts to increase their performance, speed and efficiency while decreasing the damages to the vehicle that are intrinsic to this activity. Until recently, most such vehicles were powered by gasoline engines, but the quieter, cleaner and more efficient electric vehicles are rapidly coming to the fore. The tracks designed for the radio controlled vehicles provide very rigorous set ups which cause the vehicles to go flying into the air and land hard, often from significant heights. These hard landings can cause considerable damage to the engines and transmissions of the vehicles. In previously designed vehicles either a slipper clutch or a differential transmission was used. The electric vehicles operated without a clutch causing the impact from a hard landing to be transmitted over the entire drive train.
Jenkins, in U.S. Pat. No. 5,104,361, discloses a means to adjust the tractive torque at the driven wheels of a scale model vehicle that employs an enclosed friction differential. A locking pin in the form of a hexagonal wrench having a long shank is inserted into the differential through a guide means and passes through the internal members. The first stub axle is prevented from rotating so that one driven wheel is locked while the other driven wheel is free to rotate. This is accomplished without having to disassemble the transmission and was, at the time, an improvement over the prior art.
There have also been developments in full sized vehicles to provide more efficient wheel differentiation. Holan et al., in U.S. Pat. No. 4,637,276, describe a vehicle differential having fewer gears then others of its time. In this system the right and left half axles are contained within a differential case. In one embodiment the ends of the half axles are not in contact and one half axle is driven while the other is permitted to free wheel and therefore will turn faster or slower than the driven wheel depending upon which side is turning. In another embodiment a slip clutch consisting of a plurality of clutch driving plates and clutch friction plates is contained within the differential case. The slip clutch is added to slippably couple rotatory motion from the left half axle to the right half axle. To achieve the same result, a controlled multi-disc slip clutch was added between the crown gear and the differential housing of the rear axle differential of an all wheel drive tractor as disclosed by Haupt et al. in U.S. Pat. No. 5,162,636. The slip status was regulated according to the parameters of the track radius to be executed and for the traction needed. In a more sophisticated system, the differential assembly includes a friction disc clutch assembly disposed within the differential case to selectively lock the differential assembly and a hydraulic clutch actuator to selectively frictionally load the clutch assembly. (Kaplan et al., U.S. Pat. No. 6,733,411) See also U.S. Pat. No. 6,742,640 to Grogg et al.
A spur gear differential designed for use in an all terrain vehicle has a first side gear configured to receive the first shaft for driving the first wheel and a second side gear configured to receive a second shaft for driving the second wheel. This assembly utilizes three sets of two planet gears. First planet gears engage the first side gear and second planet gears engage the second side gear. The assembly also has a clutch pack made up of a series of friction plates and reaction plates and an internal gear train in cooperation with a fly weight assembly. Though contained in a single package, this system utilizes a number of interactive parts that can become damaged or unseated under extreme off road conditions. (Maki et al., U.S. Patent Publication No. 2006/0160652)
A more recent patent (U.S. Pat. No. 7,377,295 to Byers et al.) describes a slipper clutch assembly for a fuel powered model vehicle. The slipper clutch transfers torque from the spur gear to a transmission input shaft and serves to protect the spur gear and engine from acute shocks to the drive train when the vehicle lands after a jump. The slipper clutch assembly interposes a friction coupling between the spur gear and the transmission input shaft which slips allowing the spur gear to rotate faster than the input shaft until the speed is slowed by the friction coupling.
Gasoline powered model cars require the use of a clutch, while electric model cars can utilize either a slipper clutch or a differential. There is a need for a transmission for model cars and especially for model electric remote controlled cars that combines the differential with a slipper clutch in a single compact unit to protect the engine and transmission from shock resulting from high impact landings and rigorous track set ups. There is a need for a compact transmission that not only takes up little space but is light weight and easily adjusted without having to be removed or taken apart. There is a need for a model car transmission that functions smoothly, is reliable and occupies substantially the same space as the present differential transmission in these vehicles.